Meeting the Paris Agreement on Climate: Exploiting Earth System Models to determine the role of future land-use change

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This Fellowship will exploit the next generation of climate models to make the UK's first assessment of the potential for land-use change policy (e.g., reduced deforestation and increased afforestation) to help society meet climate targets. Three years ago, an ambitious global agreement was signed in Paris to try and limit warming due to climate change to less than 2 degrees since the pre-industrial period; we're already at almost 1 degree. Scientists can use detailed computer simulations to try and understand what could happen to the climate in the future; by 2050 in scenarios that succeed in limiting warming to the levels specified in the Paris Agreement, society is no longer a net emitter of greenhouse gases (GHGs), but we are drawing more GHGs out of the air than we're putting in. The longer it takes global GHG emissions to peak the greater the extent of GHG removal, or negative emissions, we will require. There are a couple of ways that net negative emissions could be achieved. Currently, the most technologically feasible is through eliminating deforestation and engaging in large-scale afforestation and reforestation. Another way, which relies on future technological developments, is to burn biomass to generate energy and then capture and store any GHGs that would have been emitted in deep geological reservoirs. Initial estimates suggest that an area the size of Australia would need to be dedicated to growing energy crops in order to generate sufficient negative emissions through this process. My previous research has demonstrated that forests and other vegetation can have a cooling impact on the climate because of interactions between plants and the composition of the atmosphere. Plants emit a wide range of gases into the air, the kind that give pine forests their distinctive smell. These gases take part in complex chemical reactions and can go on to form particles that act as seeds for cloud droplet formation. This process is important because the more droplets there are in a cloud, the brighter and more reflective of the Sun's energy it is, helping to cool the climate. My previous work also indicates that the cooling effects due to these natural particles could become stronger as global temperatures rise; this may act to slightly dampen the warming caused by higher GHG concentrations. During my Fellowship, I will develop and use the UK's first fully-coupled Earth System Model (UKESM) to assess the potential for future land-use change to help meet global climate targets. I will work with international organisations to ensure that UKESM contains state-of-the-science understanding of biosphere-atmosphere interactions; using a fully-coupled ESM to explore this represents a step-change in the way we can evaluate impacts on, and of, future climate.